Visualization of Ice Crystal Behavior in Mouse Oocytes During High-Speed Quench Cooling and Ice Inhibition by Antifreezing Hydrogels

Oocyte vitrification has become a widely adopted method in clinical practice. However, the solidification behavior and its impact on oocytes during the ultrarapid cooling process remain poorly understood. In this study, we established a system and methodology to observe crystallization behavior in oocytes during quench cooling and warming. Subsequently, the threshold concentration of cryoprotective agents (CPAs) required for oocyte vitrification was determined through a visualization method. The results demonstrated that the ice front could not be observed in the image sequence when using 16.5% DMSO +16.5% EG during high-speed quench cooling (2821.58°C/min). Finally, oocytes were encapsulated with an antifreezing hydrogel (7.5% EG +7.5% DMSO +0.5% alginate) and subjected to high-speed quench cooling. No ice crystals appeared in the antifreezing hydrogel-encapsulated oocytes at a low concentration of osmotic CPA (2.4 M). This research opens up new possibilities for oocyte vitrification with a reduced concentration of CPA.